#include<stdio.h>
int Fid(int n)
{
    int a = 0;
    if (n == 1)
        return 1;
    if (n == 2)
        return 1;
    if (n >= 3)
    {
        a = Fid(n - 1) + Fid(n - 2);
    }
    return a;
}
int main()
{
    int n = 0;
    scanf("%d", &n);
    int ret = Fid(n);
    printf("%d\n", ret);
    return 0;
}